The majority of syringes and needles used today for medical or laboratory purposes are intended to be discarded after a single use. Disposal of the syringes and needles poses a potential hazard for the individuals who use the syringes, as well as for those people who dispose of them. With the increased awareness concerning the potential for the transmission of AIDS and other infectious diseases, a number of different protective devices have been proposed to protect the user against accidental needle sticks. Protective devices of this type for use on syringes have become known generally in the medical field as safety syringes.
A number of safety syringe constructions have been proposed which satisfy the general requirement that the point of the needle be enclosed or covered once the syringe has been used. One common feature of these safety syringes is to provide a protective sleeve which is movable between a retracted position in which the needle point is exposed and an extended position in which the needle point is protected. In many of these safety syringes, the protective sleeve includes an elongate slot which extends lengthwise along the side of the protective sleeve and is open at the distal end of the protective sleeve. Although this type of safety syringe allows the user to lock the protective sleeve in the extended position, the locking mechanism may be readily defeated by prying open the distal end of the protective sleeve to defeat the locking mechanism. Other safety syringes include protective sleeves having relatively complex twist-to-lock mechanisms and which do not readily indicate when the protective sleeve has been locked in the extended position. In other safety syringes, the protective sleeve locks automatically when the sleeve is extended. This automatic locking of the protective sleeve may result in the accidental locking of the protective sleeve in the extended position prior to the use of the syringe.
Although many of the above described devices meet the general requirements for a safety syringe, many of the proposed designs are not commercially viable because they are much too complicated to manufacture economically and efficiently. Additionally, other devices would require a modification in the conventional method of using a syringe. This is generally unacceptable due to the large amount of time and expense involved in teaching all of the potential users of such a device the proper technique in using the new device.
Therefore, it is apparent that a need remains for a safety type of syringe having a protective sleeve which will not interfere with the conventional method of using the syringe and which may be produced efficiently and economically.